In a biosensor proposed in the background art, a membrane having a reactive group selectively reacting to a specific molecule is formed on an electrode so as to measure a change in potential when the membrane adsorbs the aforementioned specific molecule. Specifically, the biosensor uses a system in which a membrane having glucose oxidase is formed on an electrode, and a change in current value caused by oxidation reaction with glucose is measured to detect the amount of glucose.
As for such biosensors, for example, refer to Japanese Patent Laid-Open No. 260156/1998; Aizawa, Chemical Communications, p.945 (1989); Alexander Star, Jean-Christophe P, Gabriel. Keith Bradley, and George Gruner, Vol. 3, No. 4, 459-463 (2003); etc.
The biosensors in the background art adopt a method for directly detecting a current value caused by chemical reaction as described above. Therefore, the detectability is so low that it is difficult to detect low-concentration glucose. In such a manner, the biosensors have a problem that they cannot show their own feature of high selectivity effectively.
An object of the present invention is to solve the foregoing problem in the background art and provide a single-electron transistor, a field-effect transistor, a sensor, a method for producing sensor, and a sensing method, having sensitivity much more excellent than that in the background art.